I added the vacuum type to my car and it works ok. As soon as the road
starts heading up the car slows and won't kick down unless I stomp on the
gas myself. Once it has kicked down the car will climb back to the set
speed without my foot on the gas and once the road flattens out it will
shift back up again. I don't know if the electric ones have the same
issue, but it's much better than nothing.